Association Between Weight-Adjusted Waist Index and Emphysema in Adults in the United States: A Cross-Sectional Study Involving 44,949 Participants

<b>Background</b>: The relationship between obesity and respiratory diseases has been widely explored. In this context, the Weight-Adjusted Waist Index (WWI) has emerged as a novel metric for assessing visceral fat. This study aims to evaluate the association between WWI and the risk of emphysema in the U.S. population, by utilizing data from the 2001-2018 National Health and Nutrition Examination Survey (NHANES). <b>Methods</b>: A cross-sectional study was conducted using NHANES data from 2001 to 2018. Logistic regression models were applied to assess the relationship between WWI and emphysema risk. Interaction and subgroup analyses were performed to explore effect modifiers. <b>Results</b>: Our study included a total of 44,949 American adults. The results of the multivariable logistic regression analysis revealed an association between WWI and the incidence of emphysema. In the fully adjusted model, the probability of developing emphysema was 1.5 times higher in the group with WWI > 10.46 compared to those with WWI ≤ 10.46, with an odds ratio of [1.5 (1.1, 1.9), <i>p</i> = 0.003]. Subgroup analysis showed stronger associations among males, non-Hispanic Whites, and individuals with hypertension. Furthermore, we used a two-piece linear regression model and found a nonlinear association between WWI and emphysema, with a breakpoint at 12.5. <b>Conclusions</b>: Our findings indicate a significant association between WWI levels and emphysema. Larger-scale prospective studies are needed to further explore the role of WWI in emphysema.